Smart spaces, such as smart homes and smart offices, have steadily gained importance in recent years. Presence detection is a new application domain which is strongly related to smart spaces. The idea of detecting the presence of moving objects by letting them cross a light beam is already known. Other presence detection systems and methods, for example based on pressure transducers, are also known.
For example, U.S. Pat. No. 7,019,641 B1 discloses a human being presence detection system which automatically determines the presence of human beings without directly attaching sensors to the human body and which detects human drowsiness. The detection system characterizes the occupancy of a vehicle seat to determine the characteristics of deployment of vehicle airbags and restraints in the event of a crash/accident. In other applications, the presence of persons hiding in a predetermined space is detected, including caves, underground bunkers, tunnels, etc. The rescue of military personnel or of persons trapped under rubble, behind barriers, within building, etc., is facilitated. In one embodiment, human beings are detected using data obtained from pressure transducers in the space of interest. The pressure signals are processed by a novel signal processing algorithm to determine the presence or absence of a human being, using information from different types of pressure transducers. In addition, the system can identify other characteristics of a human being, such as whether a vehicle seat occupant is normally seated or leaning, once it is determined that a human being occupies the seat.
Another example of a presence detection system is known from U.S. Pat. No. 6,255,946 B1, which discloses a system for detecting the presence and direction of an object passing through a gate, for example, a door of a building or a room, and announcing the detection result to the operator or persons in the building or the room. The system detects an object passing through a gate supported laterally by a frame. The system comprises a reflector, signal generating and determining means, and a user interface. The reflector is disposed at an edge of the frame. The signal generating and determining means is disposed at the other edge of the frame so as to face the reflector. The signal generating and determining means generates a first and a second infrared beams to emit to the reflector, receives a mixed beam in which the first and the second beams reflected by the reflector are superimposed, and determines the presence and direction of the object passing through the gate based on the mixed beam. The user interface notifies a user of the presence and direction of the object when the object passes through the gate and receives an operation command from the user. The signal generating and determining means comprises first and second infrared emitters for generating the first and the second infrared beams, respectively. The first and the second infrared emitters are mounted in a single housing.
These systems have the problem that they do not distinguish well between human and non-human objects. Distinguishing between human and non-human objects is an important requirement for smart spaces where specific decisions are taken dependent on the presence of human beings, for example where lamps are turned on automatically when a human being enters a room. In such a case, movement of a non-human object into a room should not trigger the lighting system to turn on the lamps automatically.